Electrical Overstress (EOS) is considered as the exposure of a device or an integrated circuit (IC) to a current or voltage beyond its absolute maximum ratings. EOS can occur due to voltage overshoots resulting in high destructive currents.
One type of EOS is Electrostatic Discharge (ESD), which is known as transfer of electrostatic charge between bodies or surfaces at different electrostatic potential. ESD can happen due to sudden discharge of charge from a charged body. The ESD occurs when differently-charged objects are brought close together or when the dielectric between them breaks down, often creating a visible spark. ESD is a high current event in the typical range of 0.1 A to 30 A in a very short period of time from 1 ns to 200 ns.
Many ICs include electrostatic discharge (ESD) protection circuits designed to protect the ICs against transient voltages such as ESD events and surges. An ESD protection circuit typically is designed to turn on during an ESD event and form a current discharge path to shunt the large ESD current and clamp the voltage of input/output (I/O) and supply pads to a sufficiently low level to prevent the IC from being damaged. The current shunting path is often provided by an active device that provides a conduction path with a relatively low on-resistance, for example. The ESD protection circuit typically ensures a low resistance path to prevent voltages from building up to potentially damaging levels.
In addition to primary ESD protection circuits described above, deep-submicron CMOS ICs typically need secondary ESD protection devices at signal interfaces between I/O and core regions or between different supply domains on one chip. Interface protection is also required for die to die interfaces when it comes to 3D integration of several chips in one package. Interface protection is typically small (compared to a primary ESD protection) but has to be placed at many locations within an IC.
Sensitive electronic components have to be protected from ESD not only during operation but also during manufacturing, assembly, shipping, and other steps during the entire life cycle of the product. For example, when a charged device is made to contact a grounded pin, for example, during packaging or assembly, the charge from the device is discharged quickly (ns range). Depending on the source of the ESD, the energy of the ESD pulse as well as the required protection are different.